Combination of AgNPs and Domiphen is Antimicrobial Against Biofilms of Common Pathogens.

Purpose: The aim was to evaluate the antimicrobial potential of AgNPs synthesized with leaf extract and investigate the antimicrobial synergistic effects of AgNPs combined with domiphen and provide an efficient and broad-spectrum combination drug strategy.

Methods: AgNPs synthesized with leaf extract were studied using UV-vis spectroscopy, FTIR spectroscopy and particle size analysis. Then, leaf extract-synthesized AgNPs and domiphen were tested against (ATCC 19606), (ATCC 6538), (8099) and (ATCC 10231), respectively. Then, we explore synergistic antimicrobial effect and synergistic anti-biofilm effect through combined drug susceptibility test and combined drug minimum biofilm eradication concentration (MBEC) test.

Results: Characteristic absorption bands of AgNPs were found near 430 nm in the UV-vis spectrum. Particle size analysis results revealed that the average particle size of leaf extract-synthesized AgNPs was 77.6 nm. leaf extract-synthesized AgNPs showed high antimicrobial activity against the above four strains. Minimum inhibitory concentration (MIC) of leaf extract-synthesized AgNPs against strains was 1 μg/mL for , 2 μg/mL for and . MBEC of leaf extract-synthesized AgNPs against strains was 2 μg/mL for , 4 μg/mL for , 1/2 μg/mL for and 2 μg/mL for . The combination of leaf extract-synthesized AgNPs and domiphen has synergistic antimicrobial effect and synergistic anti-biofilm effect. Fractional inhibitory concentration (FIC) was ≤0.5.

Conclusion: leaf extract-synthesized AgNPs had antimicrobial activity against the above four strains. The combination of leaf extract-synthesized AgNPs and domiphen has synergistic antimicrobial effects to reduce the dosage of each antimicrobial drugs. leaf extract-synthesized AgNPs and domiphen have synergistic anti-biofilm effects.